The present invention relates to the collection and removal of floating debris from water flows, and particularly from combined sewer overflows.
Trash and debris floating on the surfaces of waterways or along shorelines and beaches is a highly visible form of water pollution, which is receiving attention for its adverse, polluting effect and for its unaesthetic appearance of the surfaces of lakes and other water bodies. One type of system for the collecting and removing of floating debris has consisted of arrays of disposable mesh nets installed in receiving bodies of water in the flow path of a sewer outlet, particularly in applications referred to as xe2x80x9cCombined Sewer Overflowsxe2x80x9d or xe2x80x9cCSOsxe2x80x9d. Such systems are described in Vol. 2, No. 3, of Fresh Creek Technologies, Inc. xe2x80x9cShorelinesxe2x80x9d newsletter. Systems of this type are effective in collecting floatables or trash for removal and are shown in Fresh Creek Technologies, Inc. Netting Trashtrap(trademark) Product Bulletin. Improvements in such devices are described in U.S. Pat. No. 5,562,819, owned by the assignee of the present application, which provides an underground, in-line apparatus for trapping and collecting debris in a sewer or storm flow conduit, a secondary trap which provides continued protection when primary collection traps are full, a system which signals when primary bags or nets are full and servicing is required, and a trapping facility in which bags or nets may be replaced without loss of trapping protection during servicing.
More specifically, the device in the patent referred to above includes an enclosure or chamber with an inlet and an outlet each adapted to be connected to a sewer, storm drain conduit or outflow. A debris removing system is disposed within the chamber between the inlet and the outlet for trapping and collecting water borne debris entering at the inlet and thereby providing for an outflow of substantially debris-free water. The enclosure includes an access opening comprising upper doors or hatches or access hatches in the enclosure sized to allow the debris removing system to be removed and replaced. The debris removing system specifically includes a perforated container having an open end facing the inlet of the chamber. The perforated container includes a netting assembly that traps and collects the trash or floating debris. The container is in the form of a netting assembly having a flexible bag-shaped mesh net attached to a frame. The netting assembly is attached to lifting structure having supports or handles for allowing the frame and net to be lifted out when the net if full of captured debris. In some applications, a bypass weir or screen is provided to normally direct flows from the chamber inlet through the open end of the net while allowing flow to bypass the net and flow to the chamber outlet when the net is full of debris.
Sensing and signaling elements are typically provided for sensing and signaling the passage of solid debris around the net when the net is full of debris and is in need of servicing. The sensing and signaling elements may include mechanical structure which permits passage of water, but is displaced by impingement of solid debris flowing around the nets. Displacement of such mechanical structure signals when the net is full of debris, for example, by actuating a visible flag above ground or by actuating an electrical switch which activates an aboveground indicator or remote indicator. The sensing and signaling may include an optical sensor for detecting the passage of debris around the netting assembly. Upon detection of debris, the optical sensor emits a signal indicating that the trap is full of debris. The signal may also activate an aboveground indicator or a remote indicator.
Multiple trap systems are employed in which the enclosure includes side-by-side trap assemblies. Such systems may be configured such that, upon filling of the first trap, the flow and debris can be diverted over a bypass weir disposed between the inlet ends of the first and second traps so that flow is thereby directed through the second trap and overflow debris is trapped and collected. Closure panels may be provided in a stationary frame structure disposed adjacent the inlet ends of the traps in either the single-trap systems or the multitrap systems to restrain debris from flowing through the chamber during servicing.
Floating debris removal systems are designed to predefined peak flow rates established through monitoring and modeling based on maximum size reported storms for certain historic periods. Such modeling does not necessarily take into account the actual maximum possible amount of flow due to future record storms or particularly localized concentrations of precipitation or water flow concentration due to changing surface conditions. Bypass devices have been provided in such systems to release excessive pressures, but localized fluctuations in the flow patterns can cause imbalance forces causing premature triggering of such bypass devices. Ideal control of these devices in such situations has been lacking in the prior art.
Further, in such systems, removal from the water stream of suspended solids, particularly small suspended solids, has not been provided. In addition, in all systems of the prior art, the changing of the nets of the trap in the main contributor to the cost of servicing and maintaining the system. Accordingly, improvements in such systems that contribute to the efficiency of the net-changing task are continuously needed by such systems.
Accordingly, needs exist for improvements in such floating debris removal systems that will address the problems set forth above.
A primary objective of the present invention is to provide floating debris removal systems with the ability to handle extreme flow conditions, and, more particularly, to do so without disabling the debris removal capability of the system.
A secondary objective of the present invention is to provide such systems with the ability to more effectively remove debris from the water stream, including particularly the removal of suspended solids, such as small suspended solids.
It is a further objective of the invention to provide such debris removal systems with more efficient structures for changing of the nets of the trap.
According to certain principles of the present invention, a floating debris removal system is provided with a bypass weir or overflow screen or grate that is hinged at the top and positioned to swing downstream under certain conditions. The screen is fastened to fixed structure at the bottom with a shear ring or other shear device that will break when sufficient force is generated against the screen by the flow of overflow water and debris through the system.
According to other principles of the invention, one or more velocity dissipating members is provided adjacent the inlet. In the illustrated embodiment, one or more plow-shaped members is pivotally connected above the inlet of the system to pivot off of the bottom and open upwardly as flow increases. The plow-shaped member has, for example, a plow-shaped blade that spreads the flow across the inlet of the trap of the system to dissipate the energy of the flow and thereby reduce the velocity of the flow. The shape and weight of the blade are selected for optimal function under a range of water levels and flow velocities. The blade can be altered to perform best for different installations.
According to certain aspects of the invention, collection pits are provided before or after the traps of the system to collect small suspended solids or sediments that are not otherwise removed by the traps. The pits are sized and configured to promote the settling of suspended solids or sediments into the pits that may include objects smaller than the mesh of the nets of the traps.
In accordance with further aspects of the invention, the traps are provided with guide pins at the upstream of the traps of the frame thereof adjacent the mouths of the nets. The pins ride in vertical rails to facilitate loading and removal of the traps in the system. A third plate-like rail, preferably on the face of a service access ladder, helps guide the downstream end of the traps, while simplifying the overall construction, minimizing surfaces on which dirt can collect, and conserving space.